Speaking for liver transplants, they are a many hour traumatic affair. My daughter lost and received more than her entire blood volume during hers. Initial recovery is extremely immunosuppressed and some of the drugs we had to handle with masks and gloves, and had 4x a day medication schedules. So you couldn't burn through pig livers I believe getting them swapped frequently. My daughter received her liver at age 8 months by the way and is now 19 yrs old.

For renal transplants - not sure if there’s an upper limit, although each subsequent transplant becomes a more difficult match (as antibodies build up) and eventually may have to remove previous transplants. Generally renal transplants go in the right or left groin with native kidneys left in place. If one transplant fails, a transplant to the opposite side may be attempted, or a different location (such as intra-abdominal). Otherwise, will need to explant the first transplant